SE4109 History

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First I like to thank Mark L. Smith and Dana Scott, former ARP employees, for their contribution to the SE4109.


The first time I heard about the 4109 filter was 12 june 2004 through an email send by Dana Scott. He was thinking about cloning the 4109 filter and bring it onto the market.

A small correspondence started. But it became quiet after the last email dated 1 september 2004. I kept looking around and around. I got in contact with John Koumoutseas also a former ARP employee, who  gave me another name and emailaddress, but no luck there. No sign of that Centaur Multi-Mode Filter.

Until september 2008. I was pointed to an Odyssey with great mods done by Arp employees.  Being interested in all mods I decided to ask if there was any documentation and yes there was. For a small fee to cover the costs Mark Smith agreed to make some copies for me. Not knowing what was shipped across the ocean I started to ask more questions about Arp and I asked if he knew about the 4109 filter Dana told me about. He did and even better, those schematics were also in the post..

Lets start with the complete story of that "maxed-out-monster-Odyssey" as told by Mark.


I created the Odyssey with my friend and engineer Dana Scott. We were living in a group house of electronic and recording engineers. It was the weekend of the Blizzard of '79 when they closed the state for a week and Rt. 128 an eight lane highway, was a parking lot of snowed-in cars! Plus the house leader had let us almost run out of oil so we had to lower the thermostat to 49 degrees. So I built it that week with my wintercoat on!

I worked with Dana to expand the Odyssey to the max'. When we discovered that the Odyssey's 4 pole lowpass filter came from the famous 2500 multi-mode filter, we saw how easy it would be to expand the Odyssey's filter to six modes. The rest was pretty easy, copying the 2600's best features. I love opposite colored keys, I practiced on an organ that had them in college. I was lucky enough to find a bag of them at ARP where I worked.



Modifications front panel from left to right.

Top- Footpedal 1 out, Footpedal Vibrato out, Multiple 2 x 4or 1 x 8, Vibratopreset speeds1 & 2, slider, LFO key trigger reset or freerun, Multi-Mode Filter selector.

Next row down-- Noise white out, pink out, LFO triangle out, sine out, square out, 2 pole outs and 4 pole outs, AR out.

Next row down--Interval Latch on/off, VCO1 saw out, square out, VCO2 saw out, square out, S&H mixer out, S&H out, , Lag in, Res mod in, Inverter1 in, in, out, below that Inverter 2 in, out.

Next row down-- Portamento and 2nd voice memory on/off, Momentary Portamento switch, inputs to VCO1, VCO2, S&H mixer, VCF mixer, VCF modulation, vca modulation ADSR single/multiple trigger.

Last row down-- Pitchbend and +/-1 Octave, Main CV modulation in, Touchsensorr out, Touchsensor routing More/Off/Less, Vibrato on/off, Touchsensor in, out, Upper CV1 v/oct or 1,5 v.oct.


Mark Smith



Now we come to 2008/2009. The beginning of the SE4109. More to follow!